diff --git a/main.c b/main.c
index 2dcc1d5..e4dd7f4 100644
--- a/main.c
+++ b/main.c
@@ -48,8 +48,14 @@ static bool hpd_fwd = false; // if the I²C source line is connected to sink
 
 // if an I²C transaction started
 static volatile bool i2c_transaction_new = false;
-// if an I²C transaction with new data started
+// if an I²C transaction with incoming data started
 static volatile bool i2c_input_new = false;
+// if the byte should be programmed
+static volatile bool i2c_prog = false;
+// the address of the byte to be read or programmed
+static volatile uint8_t i2c_addr = 0;
+// the data to be programmed
+static volatile uint8_t i2c_data = 0;
 
 // blocking wait (in 10 us steps, up to UINT32_MAX / 10)
 static void wait_10us(uint32_t us10)
@@ -510,25 +516,21 @@ void awu(void) __interrupt(IRQ_AWU) // auto wakeup
 
 void i2c(void) __interrupt(IRQ_I2C) // auto wakeup
 {
-	static uint8_t addr = 0; // EEPROM address to read
 	// make copies of status registers, since some bits might be cleared meanwhile
 	const uint8_t sr1 = I2C_SR1;
 	const uint8_t sr2 = I2C_SR2;
 	const uint8_t sr3 = I2C_SR3; // clears ADDR after reading SR1
 	if (sr1 & I2C_SR1_TXE) { // transmission buffer is empty
-		// transmit next byte
-		if (eeprom_valid) {
-			I2C_DR = *(uint8_t*)(EEPROM_ADDR + addr++);
-		} else {
-			I2C_DR = 0xff;
-		}
+		I2C_DR = *(uint8_t*)(EEPROM_ADDR + i2c_addr++); // transmit next byte (even if invalid)
 	}
 	if (sr1 & I2C_SR1_RXNE) { // receive buffer is full
-		const uint8_t data = I2C_DR; // read data (also clears flag)
-		if (I2C_CR2 & I2C_CR2_ACK) {
-			addr = data; // we only take the first address byte
+		i2c_data = I2C_DR; // read data (also clears flag)
+		if (i2c_input_new) { // we just received the first byte
+			i2c_addr = i2c_data; // we only take the first address byte
+			i2c_input_new = false; // next byte is not the first
+		} else { // received data byte
+			i2c_prog = true; // notify main loop data needs to be programmed
 		}
-		I2C_CR2 &= I2C_CR2_ACK; // NACK next received byte
 	}
 	if (sr1 & I2C_SR1_STOPF) { // stop received
 		I2C_CR2 |= I2C_CR2_ACK; // this is just to clear the flag
@@ -536,11 +538,7 @@ void i2c(void) __interrupt(IRQ_I2C) // auto wakeup
 	if (sr1 & I2C_SR1_ADDR) { // our slave address has been selected
 		i2c_transaction_new = true; // notify main loop transaction started
 		if (sr3 & I2C_SR3_TRA) { // start data transmission
-			if (eeprom_valid) {
-				I2C_DR = *(uint8_t*)(EEPROM_ADDR + addr++); // transmit selected byte
-			} else {
-				I2C_DR = 0xff;
-			}
+			I2C_DR = *(uint8_t*)(EEPROM_ADDR + i2c_addr++); // transmit selected byte
 			i2c_input_new = false; // notify we send data
 		} else { // we will receive data
 			I2C_CR2 |= I2C_CR2_ACK; // ACK next received byte